Sorry for the late reply. With the save file you provided, I ran into the issue you're reporting; however, the issue was not present on a clean save for me. I think old saves are not going to be compatible with the update, unfortunately. I tried everything I could think of to fix Laya with your old save and could not. My apologies
I found a workaround for "TypeError: skill.reset is not a function" by changing one of the .json files. I can send the .json file and a save file to you. It will glitch if you try to reset skills after that, so press Esc when it shows the reset skills window. If you level up Laya enough, resetting skills will eventually work.
I could duplicate it for Sean as well. I don't have a save state for him, but I was able to workaround it the same way.